Which IM site has the greater maximum injection volume?

• A. Arm
• B. Depends on patient
• C. Buttock
• D. Both are the same

Answer: (C)

The main idea is that the amount you can safely inject IM depends on the muscle’s size and capacity. The buttock, using the gluteal muscles, is a larger muscle with more volume to accommodate a fluid dose, so it can handle a higher maximum injection volume (typically around 3 mL or more, depending on technique and patient). The arm muscle used for IM injections (the deltoid) is smaller, so the safe maximum is much lower—about 1 mL—to avoid pain, muscle damage, and risk to nearby nerves and vessels. Therefore, the buttock allows a greater maximum IM injection volume than the arm.